1. Field of the Invention
This invention relates generally to an electric jack load balancing method and device for reducing the difference in load carried by each jack of a pair of electric motor-driven jacks while adjusting the attitude of a platform.
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
Under ideal circumstances, the weight of a platform will be distributed equally amongst jacks that are adjusting the attitude of the platform by lifting and/or lowering the portions of the platform the respective jacks are connected to. If the platform and/or the load it is carrying is not balanced, one or more jacks will carry a significantly greater proportion of the load than the others, causing undue wear and tear on the more heavily-loaded jacks. System performance is best when the load is distributed equally. In practice, however, it is likely that platform loads will not always be balanced evenly. The uneven weight distribution that often results while adjusting the attitude of a platform over uniquely tilted ground is a significant problem.
It is desirable to alleviate this problem by balancing platform load amongst the jacks that are doing the work during an attitude-adjustment operation. If a given jack is bearing a significantly greater load than another, an attempt should be made to transfer the additional load onto the other jacks.
U.S. Pat. No. 5,143,386 issuedSep. 1, 1992, to Uriarte, discloses a leveling system including a plurality of jacks powered by respective electric jack motors and a controller that drives the jacks at different speeds depending on how much each must extend to level the platform. In other words, the controller adjusts individual jack speeds in accordance with which part of the platform is lowest. The controller determines how far each platform corner is from level by signals received from counters that track jack extension and interprets individual electrical jack motor current draw values exceeding one fixed, predetermined current value as indicating jack ground contact. After detecting ground contact of all jacks, the controller then continues to monitor all electric jack motor current draw values during subsequent leveling until it detects that all the jack motors are drawing higher than a predetermined low current setting indicating a level platform attitude requiring deactivation of all the jacks. However, while a leveling system constructed according to the Uriarte patent would be able to monitor the current draws of the jacks, it would be unable to use that information to prevent one or more of those jacks from carrying significantly more load than the others during leveling operations.
What is needed is an electric jack load balancing system that can prevent one or more jacks from carrying significantly more load than the others during leveling operations.